Intravascular ultrasound (IVUS) imaging has become an essential imaging modality for the effective diagnosis and treatment of cardiovascular diseases during the past decade due to innovative applications of piezoelectric transducer technology. The limitations of the same piezoelectric transducers have impeded the improvement of IVUS for emerging clinically important applications such as forward viewing arrays for guiding interventions, high resolution imaging of arterial structure such as vulnerable plaque, vasa vasorum and fibrous cap, and for implementation of techniques such as harmonic imaging of the arterial tissue and of the contrast agents. In this project, we plan to proceed on two parallel paths with immediate and long term impact. On one path we propose to develop low cost, low profile, broadband CMUT-based IVUS probes with 2 to 4 single chip annular arrays to generate M-mode slices of coronary arteries around 25MHz center frequency and 100% fractional bandwidth. These arrays will improve the crossing capabilities of IVUS catheters and can be potentially scanned and pulled back manually to generate images during interventions. Implementation and testing of these probes will enhance our understanding of issues related to the manufacturing of CMUT-based IVUS arrays and result in possible design improvements. In parallel with this effort, the second path aims to explore innovations in CMUT design to enable novel IVUS applications. CMUTs with dual electrode structures not only improve the pressure output for high penetration depth and tissue harmonic generation, but these transducers may simplify the probe electronics by removing the need for transmit-receive switching. Dual electrode CMUT structure coupled with mass loaded CMUT membranes opens up other possibilities. With enhanced sensitivity to selected harmonics based on these novel CMUTs, the proposed research may advance medical ultrasound imaging in general generating an impact much broader than IVUS. [unreadable] [unreadable]